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VETERINARY ANATOMY to protect the rectum and urinary and genital organs; also the cranial bones,to protect the vital organ called the brain. 'Irregular bones. Define anatomy. ▫ Discuss the different fields of anatomy. ▫ Identify and describe the integumentary system. ▫ Identify and describe the musculoskeletal system. Veterinary Anatomy of Domestic Mammals - Textbook and Colour - Free ebook download as PDF File .pdf), Text File .txt) or read book online for free.

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Google is proud to partner with libraries to digitize public domain materials and make them widely accessible. Public domain books belong to the public and we . PDF | On Dec 1, , Peter F. Flood and others published Textbook of Veterinary Anatomy, 2nd ed. PDF | On Jan 1, , Tootian Z and others published Basic Veterinary Anatomy.

Variation[ edit ] The sternal portion of the muscle is sometimes wanting and more rarely defects occur in the lateral part of the central tendon or adjoining muscle fibers. Development[ edit ] The thoracic diaphragm develops during embryogenesis , beginning in the third week after fertilization with two processes known as transverse folding and longitudinal folding. The septum transversum , the primitive central tendon of the diaphragm, originates at the rostral pole of the embryo and is relocated during longitudinal folding to the ventral thoracic region. Transverse folding brings the body wall anteriorly to enclose the gut and body cavities. The pleuroperitoneal membrane and body wall myoblasts, from somatic lateral plate mesoderm, meet the septum transversum to close off the pericardio-peritoneal canals on either side of the presumptive esophagus, forming a barrier that separates the peritoneal and pleuropericardial cavities.

The pleuroperitoneal membrane and body wall myoblasts, from somatic lateral plate mesoderm, meet the septum transversum to close off the pericardio-peritoneal canals on either side of the presumptive esophagus, forming a barrier that separates the peritoneal and pleuropericardial cavities.

Furthermore, dorsal mesenchyme surrounding the presumptive esophagus form the muscular crura of the diaphragm. Because the earliest element of the embryological diaphragm, the septum transversum, forms in the cervical region, the phrenic nerve that innervates the diaphragm originates from the cervical spinal cord C3,4, and 5.

As the septum transversum descends inferiorly, the phrenic nerve follows, accounting for its circuitous route from the upper cervical vertebrae, around the pericardium , finally to innervate the diaphragm. Play media Real-time magnetic resonance imaging showing effects of diaphragm movement during breathing The diaphragm is the main muscle of respiration and functions in breathing.

During inhalation, the diaphragm contracts and moves in the inferior direction, enlarging the volume of the thoracic cavity and reducing intra-thoracic pressure the external intercostal muscles also participate in this enlargement , forcing the lungs to expand. In other words, the diaphragm's movement downwards creates a partial vacuum in the thoracic cavity, which forces the lungs to expand to fill the void, drawing air in the process.

Cavity expansion happens in two extremes, along with intermediary forms. When the lower ribs are stabilized and the central tendon of the diaphragm is mobile, a contraction brings the insertion central tendon towards the origins and pushes the lower cavity towards the pelvis, allowing the thoracic cavity to expand downward. This is often called belly breathing. When the central tendon is stabilized and the lower ribs are mobile, a contraction lifts the origins ribs up towards the insertion central tendon which works in conjunction with other muscles to allow the ribs to slide and the thoracic cavity to expand laterally and upwards.

When the diaphragm relaxes, air is exhaled by elastic recoil process of the lung and the tissues lining the thoracic cavity. Assisting this function with muscular effort called forced exhalation involves the internal intercostal muscles used in conjunction with the abdominal muscles , which act as an antagonist paired with the diaphragm's contraction.

The diaphragm is also involved in non-respiratory functions. It helps to expel vomit , feces , and urine from the body by increasing intra-abdominal pressure, aids in childbirth, [7] and prevents acid reflux by exerting pressure on the esophagus as it passes through the esophageal hiatus. In some non-human animals, the diaphragm is not crucial for breathing; a cow, for instance, can survive fairly asymptomatically with diaphragmatic paralysis as long as no massive aerobic metabolic demands are made of it.

Paralysis[ edit ] If either the phrenic nerve , cervical spine or brainstem is damaged, this will sever the nervous supply to the diaphragm. The most common damage to the phrenic nerve is by bronchial cancer , which usually only affects one side of the diaphragm.

Hernias are described as rolling, in which the hernia is beside the oesophagus, or sliding, in which the hernia directly involves the esophagus. These hernias are implicated in the development of reflux, as the different pressures between the thorax and abdomen normally act to keep pressure on the esophageal hiatus. With herniation, this pressure is no longer present, and the angle between the cardia of the stomach and the oesophagus disappear.

Not all hiatus hernias cause symptoms however, although almost all people with Barrett's oesophagus or oesophagitis have a hiatus hernia. When the pleuroperitoneal membranes fail to fuse, the diaphragm does not act as an effective barrier between the abdomen and thorax. Herniation is usually of the left, and commonly through the posterior lumbocostal triangle , although rarely through the anterior foramen of Morgagni.

The contents of the abdomen, including the intestines , may be present in the thorax, which may impact development of the growing lungs and lead to hypoplasia. A large herniation has a mortality rate of three out of four, and requires immediate surgical repair. Due to its position separating the thorax and abdomen, fluid abnormally present in the thorax, or air abnormally present in the abdomen, may collect on one side of the diaphragm. It is then sometimes a space, the premolars, and finally the molars.

Some of most flexible at the neck, made up of the cervical vertebrae, and some- the more dramatic variations on this pattern are the absence of the what less flexible in the region located between the rib cage and the upper incisors and all the canines in most of the hoofed artiodactyls pelvis, made up of the lumbar vertebrae. The thoracic vertebrae, located bovids and deer , and the extreme development of the upper incisors in between the cervical and lumbar vertebrae, have the ribs attached to the elephant the tusks , the upper canines in the walrus, the self sharp- them.

There is some movement possible in this region of the spine, but much less than in the cervical and lumbar regions. The sacrum, located ening incisors in the rodents, and the canines in the warthog. Horns and antlers are sometimes found in both males and between the thoracic vertebrae and the tail, is actually several vertebrae females of the same species, and sometimes only in the males.

Horns fused together. It is rigidly locked in place between the two sides of the are present in the bovid group of artiodactyls, and consist of a bony core pelvis. The tail, when present, is extremely flexible. It is made up of the an extension of the skull covered by a horny sheath, similar in material coccygeal, or caudal vertebrae. Mammals commonly have seven cervical and origin to fingernails. They are permanent and grow throughout life. They are bar vertebrae. At its simplest, a typical vertebra can be visualized as a drum- While they are growing, they are covered with a soft skin called velvet.

Projecting upward is the The velvet dies when the antlers are fully grown for that year and is then spinous process, and projecting out to the sides are the transverse scraped off by the animal. The pronghorn antelope is notable in that processes. At the base of these projections is a hole in the bone through it has a true horn with a bony core and sheath, but the sheath is shed which the spinal cord passes. Other bony projections are present which every year a new sheath grows under the old one before it is shed.

Fibrous, elastic Horns and antlers typically arise from the skull either directly above intervertebral discs are located between adjacent vertebrae except for the eye, or more commonly from above and behind the eye. The giraffe the joint between the first and second cervical vertebrae. These horns consist of bone permanently covered with skin and fur. The rhinoceros, related to the horse group and not the artiodactyls, has one or two horns, made up of densely compressed hair with no bony core.

The first vertebra, the atlas, is the shortest. It articulates with the tail vertebrae of the various animals are buried in muscle and not back of the skull and allows for only flexion and extension of the skull. Tails are absent in apes and humans, but present in monkeys. This permits the head to tip up and down without the use of any other Tails can be prehensile grasping and hold the entire weight of a moving neck vertebrae, which means that the head can be tipped exclusively at individual.

The atlas expands into a bony wing on either side, making it almost as wide as the head—its edges can be felt below the surface, and vary in orientation obliquity among the different species. The second cervical vertebra, the axis, is the longest of all the vertebrae. It permits only side-to-side rotation of the atlas and therefore the skull in front of it.

This allows the head to rotate side-to-side without the use of the remainder of the neck vertebrae and without changing the form of the rest of the neck.

This is most dramatically demonstrated in the giraffe. The axis has a very large spinous process which expands into an upright bony plate that is aligned with the long axis of the body. While not actually sitting below the skin, but rather embedded in muscle, it nevertheless affects surface form on the back of the neck by virtue of its size. The thoracic vertebrae, especially the front ones between the shoulder blades, can have extremely long spinous processes.

For most of them, their tips usually lie just below the skin and create the profile of the animal along its back. In the horse, the spinous process of the fourth vertebra, and those behind it, are all subcutaneous; the fifth is usually the longest.

The spinous process of the fourth vertebra is where the nuchal ligament of the neck attaches, and is therefore the point at which the outline of the back of the neck meets the outline of the top of the thorax. Where the neck meets the thorax is an important point to take note of, in all animals, when the head and neck are both raised and lowered.

In the ox, the neck profile meets the back profile at the first thoracic spinous process; however, when the neck is lowered, the prominent spinous process of the seventh cervical vertebra in front of it becomes visible.

In the horse, the spinous processes in the shoulder region extend beyond the top edge of the shoulder blade and its cartilage. They are level with the shoulder blade in the dog, and lie below it in the cat. In the ox, deer, and goat, they are generally at the same level; however, in the bison, the extremely developed spinous processes extend well above the top edge of the shoulder blade.

The lumbar vertebrae have well-developed, horizontally projecting transverse processes. They project outward across the body more than the other vertebrae, and their tips can be quite conspicuous in the ox. The spinous processes above can occasionally be seen on the midline. In the horse and ox, there is limited motion in the lumbar vertebrae. In the carnivores, however, because there are more vertebrae and they are longer and narrower, this region is very flexible.

In the ox, the lumbar vertebrae, as well as the thoracic vertebrae, are oriented in a more or less straight line, which gives the animal a fairly straight profile along its back. In contrast, the lumbar region of the carnivores, along with the posterior thoracic vertebrae, arches upward. Rib cage The rib cage, which forms the chest wall, is an important volume.

Shaped somewhat like a cone, it is created by the individual ribs connecting to the spine above and to the sternum below. Its gets smaller toward the front and, in four legged animals, is flattened side-to-side. The back end is wide and open. The rib cage is wider at the top near the spine and narrower below at the sternum.

The individual ribs lie approximately parallel to each other and are directed downward and slightly backward. The lower end of each rib attaches to a flexible costal cartilage. This junction may occasionally be seen on the surface in carnivores. The ribs and their cartilages at the front portion of the rib cage attach directly to the sternum, and are called the true ribs.

The costal cartilages of the ribs in the rear portion of the rib cage angle forward to overlap the costal cartilages in front of them. Because they don't connect directly to the sternum, these ribs are called the false ribs. The cartilages of the last ribs do not attach to the cartilages of the ribs in front of them, and are referred to as the floating ribs. Carnivore ribs are slender; those of the ox are wide.

The sternum is an elongated, segmented bone located on the midline of the bottom of the thorax front of the chest. The costal cartilages of the true ribs articulate directly with it.

The sternum in dogs and cats is roughly cylindrical. In the horse, it is keel-like and flattened side-to-side in its front two-thirds. The midline of the sternum, whether flat or raised into a ridge, may be subcutaneous between the pectoralis chest muscles originating on either side of the midline. The projection at the rear end of the sternum, the xiphoid process, does not affect surface form. The front end or top of the sternum is called the manubrium.

It may be bony or predominantly cartilaginous called the cariniform cartilage. The first pair of ribs articulates with it. In four legged animals, it is either pointed or flattened side to side, and may project forward beyond the articulation with the first ribs.

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In primates, the manubrium articulates with well developed clavicles; it, as well as the rest of the sternum, is wide, flat, and faces forward. Some of the neck muscles descending from the head attach to the front or top of the manubrium or its cartilage. This junction becomes the point at which the front profile of the neck meets the profile of the chest. Called the point of the chest, it remains fixed in space regardless of the position of the head and neck, as long as the trunk remains stationary.

This point is approximately level with the point of the shoulder in horses. The depression found above the manubrium and between the descending muscles on either side of the midline at the base of the neck is called the pit of the neck.

It forms a strong, direct, bony connection the spine in four-legged animals. The scapula of the horse is elongate; between the scapula and the sternum of the rib cage.

In many four- that of the cat, rounded. A bony ridge running its length on its flat surface, legged animals, the clavicles are reduced or absent. These animals use called the spine, has a bony expansion, the tubercle, near its center.

The their forelimbs for support and locomotion, and a clavicle would trans- trapezius muscle attaches to this tubercle. The lower end of the spine of mit strong forces onto the rib cage and be either too fragile or would the scapula expands into the acromion—well developed in carnivores and interfere with function, especially when a large, heavy, running animal especially in primates, subtle in most hoofed animals, and virtually landed on its front limbs.

Therefore, they are absent in horses and absent in horses. In life, this spine may show up as a raised ridge or as a cows.

In carnivores, they are small and vestigial, persisting as small depression located between bulging muscles on either side. Its upper edge is rounded, and its back end projects rearward, beyond the back edge of the bony scapula. The upper border of the scapula including the scapular cartilage is approximately level with the tips of the thoracic vertebrae in the ox and dog, higher in the cat, and lower in the horse.

A striking difference between four-legged animals and primates is the shape, orientation, and location of the scapula. In four-legged animals, the scapula is long, narrow, oblique, and located on the side of the chest. In primates, it is triangular and located on the back of the chest, with the edge closest to the vertebral column basically parallel to it.

In four-legged animals with no clavicle, the scapula does not make a bony connection with the rib cage, but it is connected to it by muscle only. The serratus ventralis thoracis muscle, attaching to the inner upper edge of the scapula and the side of the rib cage, forms a sling that supports the weight of the body. Arm and forearm The humerus, or upper arm bone, is fairly consistent across the various species.

It varies mostly in its length and thickness relative to the other limb bones. It is short in the horse and ox, longer in the carnivores, and long and slender in primates. The upper end, the head, articulates with the scapula at the shoulder joint. The point on the outside front corner of the upper end of the humerus, although covered by thin muscle, may be seen on the surface. Called the point of the shoulder, it is an important landmark. There are two bones in the forearm—the radius and the ulna.

The radius is the weight-supporting bone in four-legged animals. In the horse and the ox, it is a strong bone that passes straight down the forearm to expand at the wrist without the presence of the ulna. The expanded upper end of the radius lies in front of the much narrower ulna. In cats and primates, the radius elbow, while the wrist end pivots around the lower end of the ulna, mov- also begins at the outside of the elbow, but it changes position at the ing from side to side. The forearm bones are oriented basically vertically wrist as it rotates around the lower end of the ulna as the forearm is in the standing position.

In some of the deer, and in goats and sheep, pronated or supinated rotated so the palm side faces forward or back. The highly developed triceps muscle of the horse will actually overhang and conceal the olecranon in the standing position when the muscle is fully relaxed. In the horse, only the upper portion of the ulna is present; its lower end tapers to a point. In the ox, the lower portion of the ulna is tapered, but it does reach the wrist. In both animals, the ulna is fused to the back of the radius.

In the dog and cat, the ulna extends down to the wrist, and is not fused to the radius. In the dog, the radius and ulna are for the most part locked in place in the pronated position, with the "palm of the paw" permanently facing backward. The cat, however, can supinate and pronate its forearm, like primates, allowing its palm to face forward or backward.

In this action, the upper end of the radius rotates in place at the outside of the appearance. The carpus contains two horizontal rows of small, somewhat cube-like bones, ranging from six in the artiodactyls, seven or eight in the horse, to eight in the cat, dog, and human. Most evident in the horse, the flexed wrist separates into three forms in front. From the top downward, they are the lower end of the radius, the top row of the carpals, and the bottom row of the carpals, which are fused by ligaments to the top of the single metacarpal.

These bones are all hinged to each other in back. The accessory carpal bone pisiform bone , part of the upper row of carpals, projects backward from the outer back portion of the wrist. Most noticeable in the horse, a strong ligament that passes downward and forward from this bone to the top of the outer metacarpal participates in creating the leg profile.

They can vary considerably—by their relative size, by some being absent, or by being fused together. Metacarpals are counted from one digits on the hand and foot. Apes and humans have long fingers on the hand and short toes on the foot. Felines have a ligament connecting the distal phalanx which sup- through five, beginning with the medial inner, thumb side. Primates ports the claw to the lower end of the middle phalanx, which keeps the have five developed metacarpals.

Dogs and cats have five, with the first claw pulled back retracted in the relaxed position. The distal pha- one reduced substantially and the second and fifth reduced slightly. This langes have to be actively flexed by muscles to extend the claws. This makes the two middle metacarpals, numbers three and four, the longest, ligament keeps the claws off the ground when felines are walking, keep- descending lower than the adjacent ones. This in turn causes the first ing their tips sharp.

When retracted, the distal phalanx becomes inclined phalanges of toes three and four to lie more horizontally than those of from the vertical, being directed upward and outward overlapping the toes two and five, which slope downward. In dogs, the tip of the claw normally Some artiodactyls, such as the ox, deer, goats, and sheep, have well-developed third and fourth metacarpals, which are fused together rests on the ground.

In the ungulates hoofed animals , the three phalanges of a digit throughout their length into a single strong bone, and are weight-bear- typically incline downward and forward in a straight line.

Exceptions are ing. Their metacarpals two and five are reduced in various ways or miss- the goat and some other hoofed animals, whose proximal phalanx is ing according to the different species, whereas the first metacarpal is inclined but whose middle phalanx is directed straight downward, giving always absent. In the horse, the third middle metacarpal, called the the foot a distinctive shape. The second and Sesamoid bones are small bones, located behind a joint, which fourth are much reduced, and the first and fifth are missing.

Metacarpals add mechanical advantage to a tendon by acting as a pulley and pushing that are reduced often have a well-developed head at their upper end a tendon slightly away from that joint. They are often located behind the and taper to a sharp or rounded point at their lower end. They are called metacarpophalangeal joints, where they have an effect on the profile of splint bones.

They are usually present at other joints of the phalanges, but Except for the first digit, each digit, or finger, typically contains three phalanges—a proximal phalanx that articulates with the bottom they do not affect surface form. An important difference between the various species is the end of a metacarpal, a middle phalanx, and a distal phalanx whose number of digits fingers or toes per hand or foot.

Because the shape conforms to the attached hoof, nail, or claw. The horse's proximal metacarpals are covered by skin and their number per foot is usually phalanx is called the pastern bone. The lower portion of its middle hidden, the exposed individual fingers or toes must be carefully count- phalanx, as well as its distal phalanx the coffin bone , is buried within ed. A horse has only one toe per limb, cows have two, rhinos three, the structure of the hoof.

In primates, eight digits per limb, making that the maximum number of fingers or the thumb is the shortest, heaviest finger, and is opposable to the other toes found in the hand and foot. Missing digits in all descending fingers can touch the other four fingers. Monkeys have long slender species were lost through evolution. Although typically the body. They are attached to each other at the midline below, and to not seen directly in four-legged animals, it is the termination of the the intervening sacrum above.

The pelvis consists of three bones—the lower profile of the belly as the abdominal muscles rectus abdominis ilium, ischium, and pubis—which are all fused together in the adult. They meet at the side of the pelvis where they form a socket, called the acetabulum, which receives the head of the femur to form the hip joint. Notice the tilt of the pelvis in the various animals by comparing the relationship between the point of the hip on the outside front corner with the ischiatic tuberosity in back.

The pelvis of the ox is more horizontal than that of the horse. The front portion of the pelvis expands into the wide, flat ilium plural, ilia. The anterior plate-like portion faces upward in the horse and ox and outward in the dog and cat.

It is especially narrow seen in side view in the cat. Its front edge, called the crest, is usually curved. The crest is concave in the horse and ox where it is covered over with muscle—concealed in the horse but occasionally visible through the muscle in the ox. It is convex and just below the skin in the dog, cat, pig, and human where it is not crossed over by muscles. The ends of the crest terminate above and below into bony landmarks whose prominence on the surface varies by species.

The point above, at the sacrum, is called the sacral tuberosity—single with a rounded point in the horse and cow, and double, but very subtle, in the dog and cat. The lower point, located toward the outside and forming the point of the hip, is called the coxal tuberosity.

It forms a simple point at the end of the crest in carnivores, a knobby expansion in the ox, and a more complicated, elongated swelling in the horse.

It is most prominent on the surface in life in the ox, visible in the horse, and subtle in carnivores. The rear portion of the pelvis is called the ischium. Its posterior projection expands into the variably shaped ischiatic tuberosity—threepointed in the ox; elongate in the dog and horse.

Called the angle of the buttocks, it can be visible on the surface in the ox, sheep, goat, and carnivores because the rear thigh muscles originate from its lower edge, leaving the upper edge exposed. In the horse, the ischiatic tuberosity is covered and concealed by the semitendinosus muscle. In the horse and ox, the width across the ilia is substantially greater than that across the ischiatic tuberosities.

In the carnivores it is the opposite, with the ischiatic tuberosities slightly wider than the ilia. Thigh The femur is the thick, heavy bone of the thigh. Projecting medially off its upper inner end, from a variably long or short neck, is the head. Humans have the longest neck, then the carnivores, and then the ungulates, where the head appears to attach directly to the top of the shaft.

The head articulates with the socket in the side of the pelvis, forming the hip joint. The outer side of the top end of the femur expands into the greater trochanter, which, although for the most part covered with thin muscle, forms a prominence on the surface. In the horse, it is completely covered by muscle of a medium thickness, but its form is still evident. Horses, rhinos and tapirs have a third trochanter—a prominent bony knob located one-third of the way down the outside of the femur, to which the gluteus superficialis muscle inserts.

The lower end of the femur expands into the spool-like trochlea in front and the two large condyles in back. The trochlea is notched in front to receive the ridge on the back of the patella kneecap. In the horse, when the knee is extended straightened , the front edges of both sides of the trochlea may occasionally be seen on the surface behind the patellar ligament.

Only the condyles, projecting backward, articulate with the tibia at the knee joint. The patella, or kneecap, glides in the groove of the trochlea when the knee is flexed and extended.

The anterior thigh muscles attach to the patella. The bottom of the patella is attached to the tibial tuberosity via the patellar ligament s. Because the patellar ligament does not change length, the distance between the patella and the tibia never changes, regardless of the position of the knee joint.

In the standing horse and ox, with the thigh relaxed, muscles or fat above the patella can overhang and conceal it. The patella is then found at the base of a depression. The tibia is a the lower leg. In the ox, only the upper and lower ends of the fibula are large bone that supports the weight of the body. Its lower end forms the present. At the upper end, the head and a very short length of the shaft entire ankle bone in the horse and ox, but only the inner ankle bone in are fused to the outside of the tibia.

The small lower end is fused to the dogs, cats, pigs, and primates, where the fibula reaches the ankle on the underside of the outer portion of the tibia. These two fibular extremities outside. The inner surface of the entire tibia is subcutaneous. The bony are connected by a fibrous cord, which is a remnant of the missing shaft prominence at its upper end, to which the patellar ligament is attached, is of the fibula.

The front edge of the upper portion of the tibia rises into a subcutaneous ridge, called the tibial crest, or shin. Two bumps may be seen on the surface on the front of the knee, especially when the knee is flexed. They are always the same distance apart, are formed by the patella above and the tibial tuberosity below, and are connected by the patellar ligament.

The tibial tuberosity is continued downward into the tibial crest.

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The full fibula is a slender bone that lies on the outside of the tibia. Its expanded upper end, the head, is an important bony landmark and does not articulate with the femur at the knee joint. Its lower end reaches all the way down to the ankle joint and forms the expanded outer ankle bone in dogs, cats, pigs, and primates. In the horse, the Hind foot The foot pes, hind foot, hind paw skeleton is made up of the tarsals, the metatarsals, and the digits, or toes.

The tarsus contains from five to seven bones. The most prominent tarsal bone is the calcaneus, or heel bone, which projects backward and upward, beyond the ankle joint, to receive the Achilles tendon of the gastrocnemius and soleus muscles. Primates and bears stand and walk with their heels on the ground; this is called plantigrade locomotion. Most four-legged animals stand and walk with only the tips of their toes on the ground and their heels raised quite high up off the ground, never touching the heel to the ground while walking; this is called digitigrade locomotion.

Muscles pull the head down; the nuchal liga- the forelimb, with some notable differences. In the horse, the single ment, along with muscles, helps raise it.

In the horse, the rear end of the nuchal ligament attaches to the Dogs may have a very rudimentary first metatarsal; occasionally, espe- tip of the spinous process of the fourth thoracic vertebra, and in the ox, cially in the larger breeds, a couple of attached small phalanges form a to the first thoracic vertebra.

This makes the neck of the horse appear much reduced digit, complete with a claw, called the dewclaw. Cats relatively longer and its trunk shorter, whereas in the ox the neck often have a tiny, rudimentary first metatarsal only, or may have a fully appears shorter and the trunk longer. In the horse, the nuchal ligament developed dewclaw.

Because these first digit bones are usually either can be seen on the surface. An elongated fat pad and the mane run absent or quite small and insignificant, carnivores are typically seen to along its upper surface.

Covered by muscle and not directly visible in the have five digits in front with a reduced first digit and four in the back. In carni- the other four digits. The big toe is the thickest toe, and is opposable it vores, the nuchal ligament is thin and has no effect on the surface. It can can touch the other four toes in monkeys and apes, but not in humans. Ligaments The sacrotuberal ligament is a sheet-like ligament in the horse The thick, strong, elastic, nuchal ligament is made up of the cordlike funicular part and the sheetlike lamellar part.

The funicular part consists of a double cable lying side-by-side that connects the back of the skull to the top of the rib cage. The lamellar part lies deep in the neck. The pelvis. The rear part of its posterior edge can occasionally be seen in the ox and the dog, passing downward and backward toward the elasticity of the nuchal ligament assists in lifting and then supporting HORSE and ox, and cordlike in the dog and feline. It connects the sacrum and the first one or two tail vertebrae to the ischiatic tuberosity of the ischiatic tuberosity.

The articular surfaces are usually covered This motion takes place only in animals with a complete ulna and with a with lubricated cartilage.

Motion takes place at joints. The motion may radius that is capable of rotation around the ulna, such as felines and pri- be slight, for instance, at the joint where a rib articulates with its verte- mates. Rotation also takes place at the joint between the first and second bra or among the small wrist bones, or the motion may be extensive, neck vertebrae the atlas and axis , permitting the head to rotate side-to- such as at the hip joint, where the thigh bone can be flexed forward, side without participation of the other neck vertebrae.

In four-legged animals, motion in the limbs is primarily flexion and Some joints have virtually no motion, such as where the pelvis articu- extension, for the purpose of locomotion. Abduction, adduction, rota- lates with the sacrum, or between the various bones of the skull. Bones tion, and gliding take place to a lesser degree.

They permit only the desired movement to take place while restricting undesired movement. Muscles The illustrations show the most important, most conspicuous move- and their tendons pull on the bones and create movement.

The degree of motion illustrated is based on Flexion takes place when two bones are brought closer together, photographs of animals in action. The left side of the body is as when bending the elbow joint so the radius comes closer to the illustrated. In most cases the horse is used, and these movements are humerus decreasing the angle between the two bones. Extension similar in the various species. Other animals are illustrated where takes place when two bones are moved further apart, as when straight- appropriate.

Each limb illustration shows only one joint moving, for the ening the elbow so that the radius moves away from the humerus sake of demonstrating that particular joint. However, in some species, increasing the angle between the two bones. Abduction involves mov- some joints always move in conjunction with others, which will ing a bone away from the centerline of the body, whereas adduction account for the skeleton appearing unnatural impossible in some brings the bone toward it.

For example, in the horse, the ankle joint must flex Rotation takes place when a bone is rotated around its long axis. Rotation occurs in the radius when the forearm is pronated and when the knee joint is flexed, and conversely, the two joints extend simultaneously. This understanding is the These muscles attach to the skeleton and create most of the surface form of an animal. The two most common types of muscles are the volumetric muscles, with full volumes, like the triceps, calf muscles, or long narrow forearm muscles, and the sheet muscles, like the thin latissimus dorsi or the trapezius.

The volumetric muscles create most of the body's forms. The sheet muscles cover the volumetric muscles and bone, whose forms may be either seen underneath or concealed.

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Sheet muscles can also produce form directly, especially at their edges where they appear in relief. A muscle belly is the total fleshy mass of a single muscle. It may consist of one or more heads, which are distinct muscle forms that usually begin separately yet have a single insertion after they fuse together.

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Muscle fibers attach either directly to the skeleton or cartilage, or by means of a tendon, which may be cable-like or sheet-like. Muscles also attach to the surface of other muscles. Fascia is a connective tissue which, among other things, forms dense, fibrous, sheets that surround the individual muscles, the limbs, and the body as a whole, forming sheaths around them.

Fascia holds the muscles in position, and yet allows adjacent muscles to glide past one another as they contract. Fascial surfaces also provide attachment areas for muscles.

When a muscle contracts and shortens, its origin and insertion get closer together and the belly becomes thick and full. When stretched, it becomes thin and elongate. One can think of the muscles of the body as a cluster of balloons attached to a rigid skeleton, all covered with a thin skin.

Regardless of whether they are volumetric and bulging, or sheetlike and flattened, they all produce convex forms. This yields a complex, undulating surface created by a series of adjacent, yet distinct, anatomical forms.

Not all surface forms conform to the delineations of the muscles as described in an anatomy book. When a muscle pulls on its tendon or on a wide or narrow fascial sheet that lies on top of other muscles, the tension across the surface can create new forms by separating the underlying muscle belly into two or more forms.

For example, the tensor fasciae latae muscle of the leg will pull on a narrow band of fascia on the outer surface of the thigh and compress the underlying vastus lateralis muscle, creating a vertical furrow.

Also, a single muscle belly can at times separate into several basically parallel bundles as it contracts. Muscle groups Muscles can be grouped into functional assemblages, which are often also visually distinct.

Throughout the regions of the body there are flexor groups, which bend the joints, and extensor groups, which straighten them. Such muscle masses usually lie on opposite sides of a bone. For example, the thigh muscles on the front of the femur together form the extensor group of the knee joint, whereas the hamstring muscles behind the femur form the flexor group of the same joint the hamstring group also functions as a hip extensor.

There are also muscle groups that abduct, or pull a limb away from the body, or adduct, pulling the limb toward the centerline of the body. Functionally opposing muscles, whether single or in groups, are called antagonists. When a body is active, one muscle group will usually be contracting and become defined on the surface, while the antagonist tends to be relaxed and less defined, or even sag.

Some muscles and muscle groups cross only one joint and perform a single action brachialis. Other muscles cross two or more joints, and can, for example, flex one joint and extend the other biceps brachii.

The next section, on individual muscles, shows each of the muscles that create or influence surface form. For each of these muscles, an illustration shows where it begins on the skeleton usually at the less mobile bone , called the origin, and where it ends usually at the more mobile bone , termed the insertion.

The positions of these attachments are quite consistent across the various species. In general, the horse is illustrated, and it is usually very similar to the ox with the major exception of the toes and the overall proportions. When the ox or the dog differ substantially, they too are illustrated. The feline cat, lion is very similar to the dog. Noteworthy differences and variations are shown or described.

The origin, insertion, action, and structure are listed for each muscle. Important differences in the other species are listed, but the common features are not repeated.

The mouth region receives the most muscles; there- masseter, and digastric and the facial muscles zygomaticus, orbicularis fore, it is the most mobile part of the face.

The chewing muscles are thick and volumetric, and they origi- Some facial muscles are so thin that they do not create any nate and insert on bone. They open and close the lower jaw, with the direct form on the surface caninus, malaris, orbicularis oculi , whereas action taking place at the jaw joint temporomandibular joint.

They originate either from the skull or buccinator, levator labii maxillaris, zygomaticus, and depressor labii from the surface of other muscles, and they generally insert into other mandibularis.

Facial muscles are generally more visible on the surface facial muscles or into the skin. When they contract, they move the fea- in the horse and the ox than in the dog and feline. The facial muscles, tures of the face eyes, nose, mouth, ears. As they pull the facial fea- as they move the eyes, nose, mouth, and ears, generate whatever facial tures, they often gather the skin into folds and wrinkles that lie perpen- expressions animals are capable of producing.

A short ligament at the inner corner of the eye, whose corner of the eye, similar to the dog. There is no levator anguli oculi inner end attaches to the skull. Eyelid portion: Outer portion: The orbicularis oculi is a flat, elliptical muscle consisting of two portions. The eyelid portion lies in the upper and lower eyelids, and the outer portion surrounds the eye and lies on the skull. The eyelid portion in the upper lid is larger than that in the lower lid. The muscle begins and ends from a ligament at the inner corner of the eye, passing uninterrupted around the outer corner of the eye.

This ligament in turn attaches to the skull, which is the only bony attachment of the muscle. Upper surface of the skull, above the eye horse , or to the rear of the eye dog. The top of the eye region, merging into the orbicularis oculi. Pulls the skin above the eye the "eyebrow" region upward, rearward, and slightly inward, creating wrinkles in the skin. This narrow muscle is an important muscle of "facial expression" as the effects of its contraction are conspicuous on the surface.

Side of the head to the rear of the eye. Outer rear corner of the eye region. Pulls the region of the outer corner of the eye rearward. The retractor anguli oculi lateralis is a short muscle. It is not found in the horse or the ox. Upper, inner, and lower edges of both nostrils from cartilage.

Front end of the forwardmost incisive bone of the upper jaw, and from a tendinous band on the midline; Insertion: Inner edge of the nostril. Dilates the nostrils. In the horse, the dilator naris apicalis is a single, rectangular muscle that spans the front of the snout from nostril to nostril. In the ox, it consists of a muscle on each side of the body that fuses on the midline.

It is not found in the dog or the feline. Surface of skull in front of the eye. Midline of snout feline, the muscle divides into a wide front portion directed downward region, beginning at the level of the eye.

Dog and feline: Snout region, and forward and a narrower rear portion directed downward and rear- just off the midline, beginning at the level of the eye. Also from in ward in the dog and downward and forward in the feline. Horse and ox: Outer edge of the nostril and the edge of the upper lip. Side of the nose and the front of the upper lip, and into the buccinator muscle. Lifts the upper lip and dilates the nostril.

Lifts the upper lip, exposing the canines, and wrinkles the skin of the snout. In the horse, the nasolabialis divides into forward and rear portions. The caninus passes between them, first passing under the narrow rear portion and then over the wider front portion. The muscle is wider in the ox; it divides into superficial and deep layers. However, the rear edge of the deep layer is exposed.

Small area of the skull deep in the back of the eye socket. Lower edge of the upper eyelid. Lifts the upper eyelid. The levator palpebrae superioris is a flat muscle that originates deep in the eye socket. It gets wider and thinner as it passes over the eyeball. The muscle ends in a thin tendon in the upper eyelid that passes among the fibers of the orbicularis oculi on its way to the edge of the lid. Lifting the upper eyelid beyond the normal open position has a dramatic effect on facial expression.

The zygomaticus is a long, narrow straplike muscle. Corner of the mouth. Into the lips as it surrounds the mouth. Also into the also just before it attaches to the corner of the mouth. It is larger in the nasal cartilage on the side of the nose.

Closes the mouth by pressing and tightening the lips. Fibers to the nasal cartilage pull the nose downward and enlarge the nostril opening. The orbicularis oris surrounds the mouth, lying in the upper and lower lips. It is continuous with the muscle of the other side in both the upper and lower lips in the horse; absent in the front of the upper lip in the ox, and separated slightly in the upper and lower lips in the dog.

The uppermost fibers reach the nose in the dog. In the horse it consists of two parts—a wide portion surrounding the lips, and a narrow portion in the margin of the lips.

This allows for greater control of lip movements in the horse. The orbicularis oris is well developed in the horse and ox, which use the lips for grazing, and less developed less mobile in the dog and feline. Lower edge of the upper jaw between the canine tooth and the molars, continuing along the tooth sockets of the molars; upper edge of the lower jaw between the canine tooth and the molars and an area to the rear of the last molar.

Edges of the tooth sockets of the upper and lower jaws. Cheek portion: Corner of the mouth, merging with fibers of the orbicularis oris. Also into the upper and lower lips lip portion. Flattens compresses the cheek, pushing food against the molars for chewing. Also pulls the corner of the mouth rearward.

In the horse, the buccinator consists of deep and superficial portions. Surface of the masseter muscle at the bony facial ridge, forms, lying between the corner of the mouth and the masseter muscle. In below the eye. Zygomatic arch and surface of the masseter muscle. Cartilaginous plate scutiform cartilage lying on the sur- fibers, and a deep portion, the fibers of which are directed forward; it can face of the temporalis muscle, located near the rear end of the upper be seen as a bulging form on the surface.

In the dog, the buccinator con- surface of the head.

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Corner of the mouth slightly toward the upper lip , merging fuse together at the corner of the mouth, and a lip portion that passes for- with the fibers of the orbicularis oris. Pulls the corner of the mouth upward and rearward. Bones of the side of the face in front of the eye in the horse; end of the facial crest in the ox; just above the large molar in the dog lower, at the end of the facial crest in the ox; above the large molar and feline.

Skin on the front of the upper lip, by common in the dog and feline. In the horse and ox, the caninus pulls the side wall of the nos- upper lip and the side of the nostril.

Muscles of both sides: Lift the front of the upper retracts the front of the upper lip, exposing the "canine" tooth. In the horse, the caninus is a thin, flat, triangular muscle. It side only: Lifts and pulls the upper lip slightly to that side. Lifts begins with a thick tendon, and widens as it inserts into the edge of the the upper lip and widens the nostril opening.

In the horse, the levator labii maxillaris is a long, teardrop- first passing under the rear portion then over the front portion. Its lower shaped muscle. It begins wide and thin, then narrows and thickens, fibers blend with the orbicularis oris; the lower edge of the muscle may be develops a round tendon, meets the tendon of the same muscle of the visible on the surface.

In the ox, the caninus does not diverge as much as other side, expands into a wide tendinous sheet, and finally inserts into in the horse, but rather develops two or three tendons that attach to the the skin of the upper lip on the front of the snout. The belly and the ten- side of the nostril. In the dog, it lies just below, and parallel to, the levator don can be seen on the surface and are directed upward, inward, and labii maxillaris; they both pass under the levator nasolabialis.

In the ox, it is a flattened muscle that passes between the two divisions of the levator nasolabialis and develops several tendons. Side of the upper jaw, at the end of the facial crest, above expanding into the wide central tendon and inserting. In the dog, the the molars. Front end of the upper lip and the lower portion of the nostril. Pulls the front end of the upper lip and the lower end of the lying parallel and above the caninus, or as the rear portion of the nostril rearward.

The muscle splits into two bundles before inserting. It is not present in the horse, dog, or feline. Front portion: The bone in front of the eye. Rear portion: Rear end of the edge of the tooth sockets of the molars of surface of the masseter muscle. Lower lip. Both sides of the head: One side only: Lifts the skin of the cheek. The depressor labii mandibularis is an elongated muscle the lower eyelid downward, opening the eye.

The two portions pull in that lies on the side of the lower jaw and runs along the lower edge of opposite directions. In the ox, the malaris is a wide, thin muscle that fans out on buccinator. In the horse, its rounded belly ends in a tendon visible on the side of the face below and to the front of the eye.

It passes under the the surface that widens as it inserts into the lower lip. In the ox, zygomaticus. The muscle has two portions—a front portion levator it consists of a muscular band with no tendon and is inconspicuous. Midline on the bottom of the lower jaw. Fascia on the bone below and in front of the eye. Into the orbicularis oculi, extending upward to the lower eyelid. Pulls the lower eyelid downward, opening the eye. The malaris depressor palpebrae inferioris is a small remnant of the usually more extensive malaris found in the other species.

In the feline, it may also lift the upper lip. The malaris in the dog is quite long, beginning at the midline of the bottom of the jaw, and extending upward to the lower eyelid.

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It passes over the zygomaticus, masseter, and buccinator. The muscle is shorter in the feline, originating from a higher level.

Side of the front end of the lower jaw near the lower canine tooth in the dog and feline. Skin of the front of the chin. Pulls the chin upward, which in turn pushes the front of the lower lip upward usually against the upper lip. The mentalis is located at the front of the chin in the prominence of the chin in the horse and ox.

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It passes downward from its bony origin to its skin insertion. The muscle fibers of both sides unite and intermingle with fat and connective tissue. In the dog and feline, the muscle fans out as it descends. Top of the skull, between the horns, and at the base of the horn.

The skin of the forehead above and in front of the eye, and into the orbicularis oculi. Lifts the region above the eye the "eyebrow" region. The frontalis, present only in the ox, is a wide, thin muscle that lies on the forehead.

The fibers that insert into the upper inner corner of the eye pull this region upward and rearward, resembling the function of the levator anguli oculi medialis which is present in the others species but not in the ox.

In the horse, dog, and feline, the muscle comparable to the frontalis is the fronto-scutularis. It inserts into, and pulls, the scutiform cartilage, which is in turn attached to the ear by other muscle. It is therefore considered one of the muscles of the ear, and not a muscle that moves the eyebrow region, as in the ox.

Assists in dilating the nostril. Upper part: From the nasal bone, along the upper edge of the horse. It inserts directly into parts of the edges of the nostril, rather than large notch at the front end of the bones of the snout to the rear of the into the outer wall of the nasal cavity.

Lower part: Both parts insert into the surface of the outer wall of the a thin muscular sheet that covers various parts of the body see page nasal cavity. Dilates the nasal cavity by pulling the soft, outer wall of the inserts into the corner of the mouth, fusing with the orbicularis oris. It nasal cavity outward and rearward, and assists in dilating the actual pulls the corner of the mouth rearward and has a strong effect on the nostril opening. It does not dilate or expand the "false nostril" nasal shape of the mouth.

It is least developed in the horse. It pulls the corner of the lies above the true nasal cavity. The lateralis nasi surrounds the bony notch of the snout and designated the depressor anguli oris. Some fibers of the cutaneous converges on the surface of the outer wall of the nasal cavity. It consists muscle of the head transversely cross over the snout and insert into the of upper and lower parts.

The upper part passes under the tendon of the upper part of the lateralis nasi. They assist in dilating the nostril. This muscle is not present in the dog or feline. The platysma of the dog is quite wide; it begins on the midline OX on the back of the upper neck and inserts into the corner of the mouth. From the edge of the top of the cartilage of the The platysma of the feline is the widest and most developed of the snout in the front of the nasal bone and just behind the nostril.

Lower species described here. It remains wide at its inserting end on the part: Along the edge of the forwardmost projecting bone of the upper side of the face where it attaches to several facial muscles, yet, as in jaw incisivus bone and the adjacent cartilage. Upper part of the inner wing of the nostril. Lower the mouth. Outer wing of the nostril. They also rotate the ear Because the ear muscles are so numerous, do not create from a forward-facing position to a rear-facing position, directing its con- surface form, and lie in layers, they are depicted here as linear axes, with cave, sound-gathering "cup" outwardly as it rotates.

The muscles insert an arrow indicating their direction of pull. The ear of the extends to be directly onto the ear, or insert onto the movable scutiform cartilage, directed horizontally, rather than upright, as in the horse, dog, and feline. Upper rear part of the skull, on the rounded braincase and the horse, a conspicuous hollow can be seen on the surface of the muscle surrounding bony ridges. It is called the "salt cellar. Top of the upward projection of the lower jaw continuing down the front edge of the jaw in the horse, dog, and feline.

In the horse and feline, the muscles of both sides meet at the midline toward the rear. Closes the mouth, for biting and chewing, by lifting the lower not meet at the midline, depending on the breed. In the dog and feline, jaw up and pulling it back. The muscle fibers begin from a wide origin and converge the muscles of both sides.